Ionic liquids are liquids that are composed entirely of ions or a combination of cations and anions. The “low temperature” ionic liquids are generally organic salts with melting points less than 100 degrees C., often even lower than room temperature. Ionic liquids may be suitable, for example, for use as catalysts and solvents in alkylation and polymerization reactions as well as in dimerization, oligomerization acetylation, metatheses and copolymerization reactions.
One class of ionic liquids is fused salt compositions, which are molten at low temperature and are useful as catalysts, solvents and electrolytes. Such compositions are mixtures of components which are liquids at temperatures below the individual melting points of the components.
Ionic liquids can be defined as liquids whose make-up entirely comprises ions as a combination of cations and anions. The most common ionic liquids are those prepared from organic-based cations and inorganic or organic anions. The most common organic cations are ammonium cations, however phosphonium and sulphonium cations are also frequently used. Ionic liquids of pyridinium and imidazolium are perhaps the most commonly used cations. Anions include, but are not limited to BF4-, PF6-, haloaluminates such as Al2Cl7- and Al2Br7-, [(CF3SO2)2N)]—, alkyl sulphates (RSO3—), carboxylates (RCO2—) and the like. The most catalytically interesting ionic liquids are those derived from ammonium halides and Lewis acids (such as AlCl3, TiCl4, SnCl4, FeCl3 and the like). Chloroaluminate ionic liquids are perhaps the most commonly used ionic liquid catalyst systems.
The alkylation of benzene with acyclic olefins is a widely practiced commercial process. This process is performed to produce a variety of chemical compounds which may be end products or may be used as intermediates in the production of other valuable industrial chemicals. One of the most significant processes for the alkylation of aromatic hydrocarbons employs liquid phase HF as a catalyst and is performed to produce alkyl benzenes which are further converted into detergents by sulfonation and neutralization.
U.S. Pat. No. 3,249,650 discloses the use of an HF catalyst for the reaction of isoparaffin and olefin. The reaction involves passing the iosparaffin-olefin stream in to an alkylation reactor along with an HF catalyst and continuously withdrawing a portion of hydrocarbon-HF mixture.
U.S. Pat. No. 3,494,971 discloses alkylation of benzene with C10-C15 olefins in two stages with hydrogen fluoride as a catalyst at 100° F. temperature. The HF catalyst employed in the first stage is a used catalyst and the HF used in the second stage is a fresh or regenerated catalyst.
U.S. Pat. No. 3,560,587 discloses the use of hydrogen fluoride catalyst for the alkylation of isoparaffin with olefin. In the process, a mixture is passed into a reaction cooler equipped with an internally placed heat exchanger, wherein the mixture is contacted with HF catalyst under isothermal reaction conditions and the reaction effluent is then passed into a reaction soaker equipped with a number of spaced perforated plates therein in which further alkylation takes place.
U.S. Pat. No. 3,686,354 discloses a method of producing high octane paraffinic motor fuel by alkylating isobutene and a C4 mono olefin in the presence of hydrogen fluoride catalyst. U.S. Pat. No. 3,713,615 discloses an alkylation fractionator having a settling section for separating liquid catalyst from the effluent of an alkylator. The lighter isoparaffins are stripped off from the heavier fractions in a fractionation section below the acid settling section.
U.S. Pat. No. 4,239,931 discloses hydrofluoric acid-catalyzed alkylation of an isobutane with a mixture of propylene and butylene at 200° F. in an isoparaffin stripping column-integrated acid catalyst regeneration system.
U.S. Pat. No. 3,950,448 discloses production of detergent grade alkylate by HF acid catalysed reaction of aromatic hydrocarbons and an olefinic hydrocarbon. The process describes the use of unique fractionation facility for the recovery and use of an aromatic concentrate and recovery of detergent alkylate product.
Use of Lewis acid catalysts has also been disclosed for alkylation. U.S. Pat. No. 3,104,267 discloses a method of preparing alkyl aromatic hydrocarbons by contacting ethylene with benzene, toluene & xylene containing catalytic mixture of titanium tetrachloride and alkyl aluminium dichloride/dialkyl aluminium chloride/alkylaluminium sesquichloride, where the ethylene is polymerized to a long chain olefin without substantial reaction of said aromatic and then contacting the reaction mixture with dry HCl/HBr, whereby the said long chain olefin alkylates to aromatic hydrocarbon. The temperature range used was 100-400° F.
U.S. Pat. No. 4,219,686 discloses a method of producing heavy alkyl benzenes and linear dodecyl benzene comprising of two steps. Auto-condensation of C11 to C14 olefins in the presence of Aluminum chloride catalyst followed by alkylation of benzene with the above reaction mixture in the presence of aluminum Chloride where the mixture is saturated with gaseous hydrogen chloride at 40-42° C.
U.S. Pat. No. 5,284,993 discloses a method of regeneration of catalyst used for alkylation of olefins by isoparaffins. The catalyst comprises of fluorosulphonic acid/triflouoromethanesulphonic acid and methanesulphonic acid. The process mainly describes the removal of acid soluble oils (ASO) produced as an undesirable by-product during the reaction. The process includes the use of water to induce the formation of the two immiscible phases of ASO and methanesulphonic acid.
US20100094072A1 discloses the use of a catalyst for the isoparaffin-olefin alkylation. The catalyst is obtained by admixing a trifluoromethanesulfonic acid on a polyacrylic acid support. It was also found that the use of solid catalysts facilitates the production of linear alkyl benzenes. U.S. Pat. No. 5,334,793 discloses the use of HF solid acid catalyst for the alkylation of benzene with olefin feed stock obtained from dehydrogenation unit containing linear paraffin having 8 to 16 carbon atoms.
U.S. Pat. No. 7,737,312 discloses the use of UOP DETAL solid acid catalyst for the production of linear alkyl benzene (LAB) from the olefin stream obtained from Fischer-Tropsch reaction. The above obtained stream is reacted with benzene to produce LAB.
Similarly, several other solid catalysts were reported so far for the alkylation reaction: U.S. Pat. Nos. 3,346,657, 4,358,628, 4,368,342, 4,513,156, 4,973,780, 5,196,574, 5,196,624, 5,344,997, 5,574,198, 5,777,187, 5,847,254, 5,894,076, 6,133,492, 7,655,824, US2011/0118517, US20110144403.
Further, several ionic liquid catalysts were reported for alkylation reaction. For instance, WO/1998/003454 discloses the use of alkyl-containing amine hydrohalide ionic liquids for the reaction of benzene with an olefin having an average carbon content of over 10, a chloroalkane having an average carbon content of over 6, or mixture thereof.
U.S. Pat. No. 5,824,832 discloses ionic liquids comprising a mixture of a metal halide and an alkyl-containing amine hydrohalide salt for the production of linear alkyl benzene. The metal halide is a covalantly bonded metal halide which can contain a metal selected from the group comprised of aluminum, gallium, iron, copper, zinc and indium.
WO/1999/003163 discloses alkylation of aromatic compounds using a catalyst which comprises a porous support impregnated with an ionic liquid consisting of an organic base and a metal. Organic base is selected from the group consisting of a halide of imidazolium, pyridinium, sulfonium, phosphonium, guanidinium, and ammonium and metal halide is selected from the group comprised of aluminum, gallium, iron, copper, zinc, and indium.
WO/2000/041809 discloses the use of catalyst comprising a pre-formed complex of an ionic liquid and an aromatic hydrocarbon for the alkylation of aromatic hydrocarbons with C2 to C10 olefin. The ionic liquid comprises a first component of the formula RnMX3—n (wherein R is a C1-C5 alkyl group, M is aluminium or gallium, X is a halogen atom) and a second component selected from the group consisting of an alkyl ammonium halide, an imidazolium halide, a pyridinium halide, a hydrocarbyl substituted quaternary ammonium halide, a hydrocarbyl substituted quaternary phosphonium halide and mixtures thereof.
U.S. Pat. No. 7,285,698 discloses a method for alkylation of isobutane and C4 olefin using a composite ionic liquid as a catalyst. The ionic liquid comprises a cation which is a hydrohalide of an alkyl-containing amine or pyridine and an anion which is a mixture of aluminum halide and halides or sulphates or nitates of copper, iron, zinc, nickel, cobalt, molybdenum or platinum.
The ionic liquid catalysts as disclosed in the prior art documents are found to be less effective when used in the alkylation reactions. Further, these known ionic liquid catalysts are expensive. Accordingly, there is felt a need for a cost-effective ionic liquid compound which can effectively catalyze Friedel crafts reactions such as alkylation reactions.